Investigatiing Whether the Thickness of Lead Inside a Pencil Affects the Resistance

Investigatiing Whether the Thickness of Lead Inside a Pencil Affects the Resistance

Aim

The aim of this investigation is to find out whether the thickness of

a lead inside a pencil affects the level of resistance when connected

to and electrical circuit.

Prediction

I think that lower resistance will be shown in the results from

pencils with thinner lead because the current will ba able to pass

through the lead easier.

Preliminary Test

Our preliminary test was for the purpose of finding out whether doing

the investigation in different ways would affect the results. We

started with putting a high current through a pencil first, taking our

results, and then lowering the voltage. Then we did the opposite,

starting with a low voltage, taking our results, and re-testing with a

higher voltage.

Diagram

page 1

Results

With the results found from the preliminary test, we decided to go

from low voltage to high voltage in the main test. This is because

when starting with a high voltage the pencil lead get hotter faster,

which affect the resistance, therefore affecting the results when a

lower voltage is tested after.

page 2

Main Investigation

Apparatus

In the investigation we used seven different pencils, labelled A to G,

an ammeter, a voltmeter, two connectors, and electrical supply and

wires to connect the circuit. (see diagram on page 1)

Method

Firstly we made the circuit as shown in the diagram on page 1, making

sure nothing was connected to the power point until the circuit was

complete. We then set the voltmeter to 1V (as close as we could get.

The reading showed 1.23V) Placing pencil A between the connectors, we

took the first reading. Whilst recording the result we removed the

pencil to prevent it from overheating, and therefore affecting the

results. When taking the second reading, we turned the pencil around

to see if that would make any difference. Again, whilst recording the